Lightweight engineering structures often suffer from environmental vibration that is difficult to suppress due to its low frequency and multiple polarizations. The emerging field of metastructure offers a practical solution for the lowfrequency vibration reduction without introducing extra isolators that have gigantic size and heavy weight. In this research, 3D printed subwavelength-scale microstructures are embedded into a honeycomb structure to form a lightweight metastructure which can suppress vibrations with different polarizations at targeted frequencies. Moreover, by simply rotating the fabricated resonators from horizontal embedment into vertical embedment, the bandgaps as well as the vibration isolations can be easily switched for different vibration sources. The multi-polarization vibration suspensions have also been demonstrated with strategically positioned resonators following interval and segment arrangements. Finally, metastructures with quasi-zero dynamic stiffness are designed to achieve the ultra-low frequency vibration isolation while maintaining their lightweight.
The overall mechanical properties of an origami can be programed by its pattern of crease, which introduces various interesting mechanical properties, such as tunable stiffness, multistability and coupled deformations. Once obtaining the knowledge about the properties of the side plates, the creases and the folding procedure, the mechanical response of origami can be completely determined. Therefore, origami with highly designable and tunable abilities offers new possibilities for the metamaterial design. In this research, we aim to combine origami with elastic metamaterials. By introducing the tunable twisting origami structure into the subwavelength-scale resonator design, a three-dimensional elastic metamaterial with low-frequency dynamic performance has been proposed, which, at the same time, has the advantages of lightweight and controllablility. The geometrical nonlinearity of the origami building block is first studied, which indicates that the large structural deformation can be harnessed to tune the effective stiffness of the origami. Further research discovers the quantitative relationship between the overall stiffness and each geometric parameter through the potential energy analysis. Then, the designed origami cell is used as an attachable resonator to control the flexural wave propagation in a metamaterial beam. Finally, both static and dynamic experiments are conducted on the origami cell and the metamaterial beam to verify the tunable stiffness and the on-demand bandgaps, respectively.